William Optics Zenithstar 103 APO
 William Optics Zenithstar 103 APOWilliam Optics Zenithstar 103 APO 

William Optics Zenithstar 103 APO

  (4 Reviews)
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About this product

Model:  wo_zs103_gd
Part Number:  A-Z103II-GD

Latest model includes new CNC-machined handle/bar (enables you to slide a William Optics Uniguider directly into the handle) & Soft Case. 

The William Optics Zenithstar 103 APO features an air-spaced doublet lens with an Ohara FPL-53 ED glass element and fully multi-coated optics for high resolution, high contrast images virtually free of false-colour. 

Despite it's large 103mm objective diameter it is surprisingly compact and very solid! Many airlines will accept it as carry-on luggage. An ideal size for serious observations of deep sky objects and planets.

Versatile f/6.9 native focal ratio or f/5.5 when used with matching 0.8x flattener / reducer.

CNC machined aluminium for a superior fit and finish. 

Heavy duty, dual speed 2.5" 1:10 R&P focuser. A popular choice for imaging.

Available in Blue, Red or Gold anodised.  

Ohara FPL-53 vs FPL-51 ED Glass

The dispersion properties of ED and SD glass elements are important in determining the overall colour correction. The abbe index is used to quantify the 'partial dispersion' of a particular glass. Pure Fluorite offers the highest partial dispersion at around 94.99 V, Ohara FPL-53 glass is very close to Fluorite at 94.93 V and is often referred to as Synthetic Fluorite.  FPL-53 is also noticeably better than Ohara's lower spec' FPL-51 glass which offers an abbe index of 81.54 V.


  • 103mm f/6.9 Doublet air-spaced APO
  • CNC machined ultra-high precision lens cell
  • FPL-53 ED glass element for enhanced colour correction
  • 2.5" Heavy Duty, dual-speed rack & pinion focuser
  • 0.8x Reducer / Flattener available separately
  • Innovative Bahtinov mask cover included!
  • Supplied with mounting rings, CNC-machined handle/bar, Vixen-style dovetail bar, Bahtinov mask cover & soft case. 

Telescope Field of View Simulator

What's in the box

  • Telescope OTA
  • Mounting Rings
  • Carry Handle
  • Vixen-Style Dovetail
  • Bahtinov Mask Cover
  • Soft Case


Aperture 103 mm
Focal Ratio F/6.9
Focal Length 710 mm
Objective Type ED Doublet, Air Spaced,
Fully Multi-Coated, SMC coating.
Lens Shade Retractable
Tube Weight 9.6lbs. (4.36 kg) - Including dovetail & Handle

Customer reviews

Average Rating (4 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
Best decision I ever took
Saturday, 18 July 2020  | 

I have owned my WO 103 for 9 months now and never cease to be amazed by its performance. It sits on a Celestron AVX which some people don't rate but it performs fine for me. I have now added an ASI183 MC Pro cooled camera and I use a WO guidescope with ASI120 mini guiding. However my experience has taken a massive step up with the purchase of the ASIAir Pro processor. Now I think I will get the best out of my investment. I cannot stress the amount of enjoyment and pleasure I am getting from my setup. Thank you FLo for your support.

Rating (max 5):  
Fantastic well made precision instrument.
Tuesday, 26 May 2020  | 

My new scope arrived today so not yet been able to give it first light. First impressions are of a superbly crafted precision instrument. The double speed focusser now has a screw on stainless steel cover which is a massive step up from the push on black plastic one supplied with the 2019 ZS73.
The scope also has all the screws and fasteners that are needed to bolt on any peripherals. The handle has a sectioned slot machined in which is intended to take the William Optics guide scope or guide scope rings on a saddle.
All moving parts move very smoothly with solid precision reminiscent of a swiss clock. There is a field rotator built in to enable turning the camera. I bought the field flattener/reducer which was fitted in a couple of minutes after following the excellent instructions. If however you want to use it visually there is a 2” or 1.1/4” rotalock.
Of course there is a transparent Bahtinov mask behind the screw on cover in the end cap as seems to be standard now with new WO scopes..

The package included a zip fastened carrying case with detachable strap which is lined with solid foam that all William Optics products are supplied in. There is plenty of space in the foam to store extras such as the flattener, filters, lenses etc. There is also a compartment in the lid to store thinner items. This came as an unexpected surprise as a previous reviewer said a case wasn’t available.
I can’t wait to try the scope out but shall have to wait until the clouds clear.

Rating (max 5):  
Zenithstar 103
Friday, 14 February 2020  | 

The telescope arrived in good condition. its a wonderful telescope and very pleased with it. pity they dont do a travel bag for it.

Rating (max 5):  
WO Zenithstar 103
Monday, 22 July 2019  | 

Scope arrived last week. I have only had a few days to play with it and very little time under the stars. It is a beautiful looking instrument and feels very solid. Nice smooth focuser and dew shield. I managed to get a quick look at the Moon and Jupiter. The Moon shows no obvious CA in the center of the FOV but does show some CA toward the edge of the FOV. Jupiter showed noticeable CA but it is very low down, the seeing was poor and the scope had not cooled down. The planet itself was quite sharp with detail though. A bit more CA than I had hoped for but it seems well controlled. Stars are tack sharp across most of the FOV. Looking forward to testing it fully when the nights get a bit longer.
The scope rests on my Skywatcher AZ4 mount with no difficulties and is easily transported outside fully assembled. It makes a great addition to my 127mm Mak as a grab and go instrument.


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